Electrical-spray vehicle has lower oil wear and lower exhaust gas emission than carburetor vehicle. But the oil wear of electrical-spray vehicle is very large, its average value of effective thermal efficiency is only 26%, exhaust pollutant does not satisfy the uprising requirements of environment protect standard. For improving effective thermal efficiency and reducing the exhaust pollutant emissions, Pat No. ZL96106780.2, issued Jul. 10, 1996, discloses a method and apparatus that make fuel of gas engine of carburetor denatured burned, however which have the following disadvantages: Firstly, using the recovered tail gas and cooling water to heat catalytic stack can't maintain a constant temperature, that result in the amount of catalytic stack is unstable fission and further result in the rotate speed of internal combustion engine is unstable; Secondly, as the front of catalytic stack has not set return oil loop, it's difficult to adjust the proportion of mix gas within internal-combustion engine appropriately; Thirdly, the apparatus's structure is complex and can not used with electrical-spray vehicle and diesel oil carburetor cooperatively.